This invention concerns improvements in wheelchairs, and more particularly relates to an improved wheelchair wherein the wheelchair-reliant person can without assistance modify the dimensional and mobility characteristics of said wheelchair.
Wheelchairs are generally constructed having a pair of small forward wheels, each supported by an overhead pivoted yoke which permits the wheel to turn 360.degree. about a vertical axis, and a pair of opposed large rear wheels positioned at each side of the chair on horizontally disposed axles which permit rotation of said rear wheels in fixed vertical planes. The rear wheels, when simultaneously pushed or pulled by the disabled occupant propel the wheelchair in forward or rearward directions.
When one rear wheel is pushed more than the other, or when one rear wheel is pushed while the other is maintained motionless or pulled in the reverse direction, the wheelchair can be made to perform turning motions. One motion however, that the conventional wheelchair is incapable of is a lateral or sideways translational motion in the direction of th horizontal axles of the rear wheels. Such sideways motion is particularly valuable in confined quarters such as an office, workshop or factory environment which cannot accommodate the size or turning radius of the large rear wheels, and where omnidirectional movement is necessary. Such omnidirectional movement, where allowed by the wheelchair, would be caused by the seated occupant by exerting pulling or pushing force against stationary objects within his reach.
Wheelchairs having removable rear wheels have been disclosed in U.S. Pat. No. 4,098,521 to Ferguson et al. The feature of optional removability of the rear wheels affords the following advantages:
(a) easier storage of the wheelchair, particularly in an automobile, PA1 (b) eliminates the need of the user to lift or be lifted above the top of the rear wheels for sideways transfer from or to the seat which is generally below the top of the rear wheels, and PA1 (c) narrowing of the lateral size of the wheelchair, thereby facilitating passage through narrow aisles. PA1 (1) It provides a wheelchair which can be converted to a mode having omnidirectional movement. PA1 (2) Said conversion can be achieved by the occupant of the wheelchair without aid, and preferably by way of a single rapid manipulation. PA1 (3) The above two features can be accomplished by virtue of a mechanical device attachable to conventional wheelchairs. PA1 (4) When the wheelchair is in its omnidirectional mode, the large side wheels can optionally be removed by the occupant without aid, causing the wheelchair to have a narrower configuration better suited for negotiation of narrow passageways.
Although the Ferguson wheelchair permits removal of the large rear wheels while the occupant is seated in the wheelchair, said removal of the wheels cannot be done unaidedly by the seated occupant himself. Another person is needed, who will stand behind the wheelchair and push down on its framework to cause a rearward tilting movement that lifts the drive wheels off the ground. Only when such tilting motion is provided by another individual, can the drive wheels be removed. Also, the same assistance will be needed by the wheelchair occupant when it is desired to have the drive wheels re-installed. Once the drive wheels are removed from the Ferguson et al wheelchair, it is of narrower width, but still lacks omnidirectional movement. Therefore, Ferguson et al expresses the concept of narrowing the width, but is completely silent on the concepts of: (a) enabling the occupant to unaidedly remove and replace the wheels, and (b) causing the wheelchair to be omnidirectional once the drive wheels are removed
It is accordingly an object of the present invention to provide a wheelchair having opposed large rear wheels mounted on horizontal axles, said wheels being removable and re-installable by the seated occupant of said wheelchair without assistance from others.
It is a further object to provide wheelchair of the aforesaid nature wherein said wheels may be safely removed by said occupant unaidedly by the performance of two separate and sequential manipulations.
It is another object of this invention to provide a wheelchair capable of motion in the direction of said horizontal axles.
It is a further object to provide a wheelchair of the aforesaid nature which, by a single manipulation rapidly achievable by the seated occupant, can be modified so as to have omnidirectional rolling mobility.
It is a still further object of this invention to provide apparatus which can be attached to a conventional wheelchair to achieve the foregoing objects.
These objects and other objects and advantages of the invention will be apparent from the following description.